Distance

Mass

Size

Discovery Methods

NGC 2273

NGC 2273 is like two spiral galaxies in one, with a supermassive black hole sitting in the middle of each of them.

The galaxy itself is classified as a barred spiral, which means it has a central "bar" of stars with spiral arms extending from the ends of the bar. High-resolution images, however, show that a smaller spiral inhabits the bar.

The black hole is at the center of this spiral within a spiral. It produces enormous amounts of radio energy, which tells astronomers that it is feeding vigorously. As gas and dust spiral toward the black hole they form a large, hot disk around it. Some of the disk material is funneled into jets that shoot into space from above the black hole's poles. Material in the jets produces radio waves.

A larger disk, which extends almost one light-year away the black hole, contains water molecules. As they're zapped by energy from the black hole's accretion disk or nearby stars, they're boosted to a higher energy level, causing them to emit microwaves. Large blobs of these water molecules produce powerful microwave beams known as masers.

Precise tracking reveals the masers' motion around the center of the galaxy. Applying the laws of orbital motion allows astronomers to determine the precise mass of the central object. If the object is massive enough and confined to a small enough volume, it can only be a black hole.

Using measurements made from 2005 to 2009, a team of astronomers determined the masses of the supermassive black holes in seven galaxies, including NGC 2273.

Their work showed that the black hole is about 7.5 million times as massive as the Sun, or roughly twice as heavy as the black hole at the center of the Milky Way galaxy.

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